Evaluation of the host immune response and functional recovery in peripheral nerve autografts and allografts.

Allogeneic peripheral nerve (PN) transplants are an effective bridge for stimulating regeneration of segmental PN defects, but there are currently no detailed studies about the timeline and scope of the immunological response for PN allografting. In this study, the cellular immune response in PN allografts and autograft was studied during the acute and chronic phases of a 1.0 cm critical size defect in the rat sciatic nerve at 3, 7, 14, 28 and 98 days after grafting autologous or allogeneic nerves without any immunosuppressive treatment. The assessment was based on functional, histomorphometrical and immunohistochemical criteria. Results showed modestly better functional outcomes for autografts with coordinate and adaptive immune response represented by the presence of CD11c, CD3, CD4, NKp46 and CD8 cells at 3 days, CD45R positive cells and CD25 positive cells at seven and CD45R positive cells at 14 days which seems an adaptive immune response. In contrast, allograft in the early time points showed innate immune response instead of adaptive immune response until day 14, when there was some increase in cell-mediated immunity. In conclusion, in PN autografts the immune system is synchronic initiating with a more robust early innate response that more rapidly transitions to adaptive while for PN allografts the infiltration of immune cells is slower and more gradually progresses to a moderate adaptive response.